A contactless power transmission device that uses a magnetic field resonance has been known as a common technique for a contactless power transmission device, which does not use a power supply wire, a power transmission cable or the like. For example, a contactless power transmission device described in Japanese Laid-open Patent Publication No. 2009-106136 includes a power supplying device that includes an AC power supply and a primary resonance coil, which receives an AC power from the AC power supply. The contactless power transmission device includes a secondary resonance coil arranged on a vehicle that enables the magnetic field resonance with the primary resonance coil. When the magnetic field resonance occurs between the primary resonance coil and the secondary resonance coil, the AC power is supplied from the power supplying device to the vehicle. The AC power is used for charging a vehicle battery, namely a variable load, arranged on the vehicle.